Add example: Bun HTTP server showcasing jrx JSX-to-JSON rendering

Bun React app with HMR that demonstrates jrx's render() pipeline.
Shows JSX source, live UI via @json-render/react, and JSON output
side by side.

- example/specs/simple.tsx: flat Stack > Text + Button
- example/specs/full.tsx: nested layout with state, events,
  visibility conditions, and watchers
- Uses defineCatalog + defineRegistry from @json-render/react
- Fix package.json exports to match actual tsup output (.js/.cjs
  instead of .mjs/.js)

Co-authored-by: Ona <no-reply@ona.com>

example/package.json

@@ -0,0 +1,23 @@
+{
+  "name": "jrx-example",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "bun --hot src/server.ts",
+    "build": "bun build ./src/index.html --outdir=dist --sourcemap --target=browser --minify",
+    "start": "NODE_ENV=production bun src/server.ts"
+  },
+  "dependencies": {
+    "jrx": "file:..",
+    "@json-render/core": "0.10.0",
+    "@json-render/react": "0.10.0",
+    "react": "19.2.4",
+    "react-dom": "19.2.4"
+  },
+  "devDependencies": {
+    "@types/bun": "latest",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "typescript": "5.9.3"
+  }
+}